Electrotherapy system



July 9, 1963 B, w. GRIFFITH, JR 3,096,768

ELECTROTHERAPY SYSTEM Filed May 2?, 1960 44 4., mmf@ United States Patent ii ice 3,096,768 Patented July 9, 1963 3,096,768 ELECTRTHERAPY SYSTEM U Benjamin Whitfield Grifth, lr., Dallas, Tex., assigner, by mesne assignments, to Firmatron, Inc. Filed May 27, 19.60, Ser. No. 32,279 2 Claims. (Cl. 12S-422) This invention relates to means and apparatus for the application .of currents o-f various frequencies to the body in order t-o excite the natural physiological response frequency of the nerves.

From the earliest times Iof electrical knowledge, the response of organic tis-sues to the stimulus of electric current has been known. The first 'detailed scientific investigation of these effects was performed in Italy yby Luigi Galvani, Professor of Anatomy at the University of Bologna. Due to the primitive state of development of electrical equipment in his era, his work was of necessity limited to the appli-cation `of 'steady-state D.C. and very low frequency (manually pulsed) A.C. Galvani also observed and investigated the effect upon organic tissue of the induced energy resulting from the spark discharge of a nearby electrostatic generator, such discharges being largely loscillatory in nature yand containing components of several frequencies.

Much Work was performed during the 19th century by many Workers in applying electric currents to the human body for medical purposes, with study being devoted to the effects of various intensities, frequencies, directions of current flow, and electrode arrangement. In 1922, U.S. Patent 1,425,743 was issued to S. N. Baruch covering apparatus which produced an alternating electrostatic eld .of a plurality of different frequencies, so that a heterodyne effect was produced. Baruch made use of the now-obsolete spark oscillator as his source of high frequency energy, [and utilized two rotary interrupting devices to produce two different frequencies of modulation simultaneously. In the applicatio-n of his invention, Baruch applied his mixed frequencies to a pair of insulated condenser plates, one of which was placed under the patient andthe other over him. According to Baruch, the body of the patient formed the condenser dielectric, in which dielectric hysteresis losses took place, thereby affecting the general metabolism of the patient.

French Patent 859,618, published December 23, 1940, describes a method which comprises the application to the body of two high lfrequency currents which intersect leach other .at tissue to be treated. The frequencies of the currents differ somewhat, so that, upon intersecting they create a beat frequency which is equal to the difference between the two high frequency currents. Such a beat frequency was found to cause a muscular contraction. A similar method was developed by Dr. Hans Nemec, and is described in his U.S. Patent 2,622,601, issued December 23, 1952. However, both the French patent and the Nemec patent describe apparatus which includes two separate oscillators for the two high lfrequency currents. The Nemec patent describes the use of a variable capacitor for varying the frequency of one current with respect to that of the other so that the frequency of the heterodyne effect in the body can be varied. The natural frequency drift of the oscillators makes it quite diicult to maintain the desired beat frequency. It is apparent that where two oscillators operating at, for example, 4000 cycles and 4010 cycles per second must be maintained at just l cycles frequency difference, a drift of just 0.1% in frequency of each oscillator will cause a wide variation in the beat frequency. The accurate maintenance of such a small `difference between two high frequencies is therefore extremely dicult, while it has been shown that the stability and -controllability of the Vbeat frequency is quite important in therapeutic applications.

It is an object of this invention to provide means for accurate maintenance of beat frequencies in electrothenapy systems.

It is another object to provide an electrotherapy system which utilizes only one high frequency oscillator and one oscillator operating Iat the desired beat frequency, the second high frequency 'being produced by the use of balanced modulators for the 'suppression of a carrier `and one side band,

Another object is to provide an electrotherapy system in which the variation of the beat frequency produced is dependant solely on the stability of a low frequency oscillator.

A further object is to provide an electrotherapy system which utilizes a circuit which is readily adaptable to the use of transistors and other semiconductor devices las well as to vacuum tube application, so that battery-operated equipment operating on these principles ca-n readily be produced.

The accomplishment of these `and other objects of the invention will become more apparent upon consideration of the following description and the accompanying drawings, wherein FIGURE 1 is a schematic diagram of one embodiment of the invention,

FIGURE 2 is a schematic diagram of another embodiment of the invention,

FIGURE 3 is a diagram `of one form of balanced modulator suitable for use in the system of this invention, and

FIGURE 4 is a diagram of another form of balanced modulator.

A balanced modulator is a circuit wherein intermodulation of two frequencies may be accomplished, with one of the `frequencies being suppressed in the output of the circuit. Such a device is used in the system shown in FIGURE 1, wherein the outputs olf a high frequency oscillator 10 and of a low frequency oscillator 12 are fed into the carrier and signal inputs, respectively, of the balanced modulator 14, wherein the low frequency signal is modulated upon the high frequency carrier. The carrier, or high frequency, is suppressed in the process of frequencies equal to the sum and difference of the two frequencies. These two frequencies are therefore just above and just below the original carrier frequency, fand their ldifference is equal to twice the original low frequency signal. In the embodiment shown in FIGURE 1, these two frequencies are ydelivered on a single circuit to a single pair of insulated electrodes 16, which are applied to the body for therapeutic purposes.

When it is desired that the two high frequencies produced be on two separate circuits, and therefore applied to separate and independent pairs of electrodes, the present invention contemplates an arrangement asis shown in FIGURE 2. A balanced modulation system of this type type is disclosed :by Hartley in his Patent No. 1,666,206, granted April 17, 1928. in Ithis embodiment of the invention, the outputs of the high (frequency oscillator 10y and of the low frequency oscillator -12 are each split into two currents which yare phased apart, this being accomplished by phase splitting networks 18, 20, the construction and operation of which are well known in the art. One high frequency current becomes the carrier input to balanced modulator `22, and is modulated by one of the low frequency currents, which is utilized as the signal in modulator 22. The high frequency and low frequency signals, shifted 90, are similarly fed into modulator 24.

The combining of the outputs of these Itwo balanced moduiators results in the suppression of the `carrier and one sideband, leaving the other sideband, which has a frequency equal to either the sum of or the difference between the Ihigh and low frequencies.

This sideband frequency is then supplied to a pair of insulated electrodes 26, 28. An `additional output from the high frequency `oscillator is applied .to a separate pair of electrodes 30, 62.

When electrodes 26, 28, 30, and 32 are applied to the body, the two different frequency currents supplied intersect `at a point within the body, .so as to generate a -beat -frequency Ior heterodyne effect within the tissue of the body, the beat frequency being equal to the loW frequency input to the balanced modulators. It will be apparent therefore that this beat frequency can be very accurately controlled, since it is affected only by variations in the low frequency input. Using the example set forth Ihereinbefore, if the high frequency used is 4-000 cycles and the beat frequency desired is l cycles per second, -a drift of 0.1% in the low frequency input would cause a variation of only 0.01 cycle per second in the beat frequency. Drift of the high frequency input will have no effect whatsoever on the beat frequency.

A wide range of frequencies have been used for electrotherapy treatments such as those for which the apparatus of this invention is suited. Normally, however, beat frequencies of from l1 to about 100 cycles per second are found most useful. The high frequency carrier input is usually from about 1000 to about 10,000 cycles per second.

In FIGURE 3 is shown a form of balanced modulator utilizing a diode ring connection which is suitable for use in the apparatuscf-this invention. vIn this 4form of 'balanced modulator the secondary coil 34 of the low frequency signal input is connected to the primary coil 36 of the output through a. diode ning 33, and the secondary coil 40 of the high yfrequency carrier input is connected by center taps to coils 34 and 36.

The balanced modulator shown in lFIGURE 4 illustrates one form `of modulator which utilizes transistors. In this construction, the secondary coil 42 of the low frequency signal input is connected to the primary output coil 44 through triode transistors 46, and the secondary coil '48 of the high frequency carrier input is connected by center taps to coils 42 and 44.

lllt will be apparent that the phase splitting networks 18 and 20 will, from their separate terminals, provide currents to the inputs of modulators 22 and 24, such that these currentsvwill differ in phase by 90.

The apparatus of this invention thus provides a comparatively simple means 'for the application of electric currents for therapeutic purposes in which the frequency of stimulation of tissue may be very accurately controlled. The circuit is readily adaptable to the use of transistors or other semiconductor devices as well as vacuum tubes, so that portable battery-operated equipment can readily be produced. Such apparatus is useful for stimulating various tissues and structures of the body to relax such tissues and to improve the tone and gen- -eral health of bodily parts.

A particularly advantageous form of treatment is one in which the electrodes lare mounted in gloves made of an insula-ting material, so that the therapist may properly direct the pulses from the electrodes to the body part or tissue which is to be stimulated by the pulses.

Although several embodiments of this invention bave been shown and described, the invention is limited Aonly as set forth in the following claims:

1. A-n electrotherapy system comprising a :high `frequency source, a low frequency source, a phase splitting network coupled to each of said sources adapted to split ythe current from each source into -two currents phased v" apart, a balanced modulator adapted to receive one of the high .frequency .currents as a carrier and one of the low frequency currents as a signal, `a second balanced modulator adapted similarly to receive the remaining two currents, means for combining the outputs of the two modulators, a pair of insulated electrodes adapted to receive the `combined .outputs of the two modulators, and

a second pair of insulated electrodes adapted to receive current directly from the high frequency source.

2. Electrotherapy apparatus including a high frequency signal source, a low frequency lsignal source, a balanced modulator coupled to each of said signal sources for providing a single sideband signal output, and a .pair of electrodes coupled to the output of said balanced modulator, said electrodes being adapted to contact a patient to ,provide a substantially constant beat frequency signal which is independent of the physiological manifestations of the patient.

References Cited in the file of this patent UNITED STATES PATENTS 

1. AN ELECTROTHERAPY SYSTEM COMPRISING A HIGH FREQUENCY SOURCE, A LOW FREQUENCY SOURCE, A PHASE SPLITTING NETWORK COUPLED TO EACH OF SAID SOURCES ADAPTED TO SPLIT THE CURRENT FROM EACH SOURCE INTO TWO CURRENTS PHASED 90* APART, A BALANCED MODULATOR ADAPTED TO RECEIVE ONE OF THE HIGH FREQUENCY CURRENTS AS A CARRIER AND ONE OF THE LOW FREQUENCY CURRENTS AS A SIGNAL, A SECOND BALANCED MODULATOR ADAPTED SIMILARLY TO RECEIVE THE REMAINNING TWO CURRENTS, MEANS FOR COMBINING THE OUTPUTS OF THE TWO MODULATORS, A PAIR OF INSULATED ELECTRODES ADAPTED TO RECEIVE THE COMBINED OUTPUTS OF THE TWO MODULATORS, AND. A SECOND PAIR OF INSULATED ELECTODES ADAPTED TO RECEIVED CURRENT DIRECTLY FROM THE HIGH FREQUENCY SOURCE. 